Newborn shoots are best taken in the first two weeks and preferably within the first 10 days. As such I would recommend booking after your 20 week scan. However, please do get in touch if you are further into your pregnancy or if you have already had your baby and I will do my best to fit you in.
For location shoots, my weekend slots get booked up very quickly so the sooner you book, the better chance you have of securing your preferred date.